[laddoo12]

Wel my prof really didn't explain anything when we were doing isomers and i had to research isomers myself
zoo what i don't get is what exactly a optical isomer is
from what i have googled i think it could be a compound that is not superimposable?
could someone actually explain what a optical isomer is in detail?

[Dan]

Optical isomerism is synonymous with stereoisomerism, the latter being IUPAC's preferred term.

Stereoisomers have the same molecular formula and the same atom connectivity. They fall into two categories:

1. Enantiomers: A pair of enantiomers is two compounds that are related as non-superimposable mirror images - so they are the mirror image of each other but they're not the same. If you have trouble seeing this, then build models. The normally cited example is your hands - they are non-superimposable mirror images.

2. Diastereoisomers: Two molecules are said to be diastereoisomers if they are non-superimposable non-mirror images, so if they are stereoisomers that are not related as enantiomers. An example would be the diastereomeric sugars glucose and mannose.

Stereoisomerism can get complicated quite quickly, depending on how far in you go. Have a read, build some models, and if you have more specific questions then it will be easier to help you. I'd recommend having a look at the stereochemistry chapters of any good general organic textbook - Clayden, Greeves, Warren & Wothers for instance - any general organic text will have the basics of stereochemistry.

See also: The IUPAC stereochemical terminology page